Electromagnetic reed switch



Jan. 11, 1966 M. J. SAKATOS 3,229,063

ELECTROMAGNETIC REED SWITCH Filed Dec. 11, 1963 4 \0 3 IV-l C} BY M/CHAEL 5213305 United States Patent 3,229,063 ELECTROMAGNETIC REED SWITCH Michael J. Sakatos, Union, N.J., assignor to General Reed Company, Metuchen, NJ., a corporation of Delaware Filed Dec. 11, 1963, Ser. No. 329,776 Claims. (Cl. 200-87) This invention relates generally to magnetic switching devices and more particularly to a new and improved magnetic reed switch which combines extremely small size with high efficiency and contact life reliability.

Magnetic reed switches are generally known in the art for controlling electrical circuits, and exemplary reed switches are disclosed in the prior patents to Ellwood, No. 2,289,830 and Karrer, No. 2,922,856. Such reed switches generally comprise a plurality of spaced-apart contact reeds positioned within an evacuated or gas-filled sealed glass tube and an outer electromagnetic coil around the tube for effecting contact switching functions in response to the selective application of switching current to the coil.

Those skilled in the use of prior art reed switches appreciate that a high mutual capacitance may exist at overlapping end portions of the contact reeds within the tube. As such, the use of such-switches in high frequency circuits and environments may be subject to undesirable limitations.

It further will be appreciated that the problem of contact sticking in the reed type switches can lead to inability of switching functions, and that various expedients have heretofore been suggested in an attempt to overcome this problem. In addition, prior art reed switches generally have not maintained a relatively equalized and maximum gap between the normally open and the normally closed reed contacts, or provided a magnetic flux concentration between the normally closed contacts to obtain highly desirable repulsive magnetic forces therebetween.

Accordingly, it is a general object of this invention to provide a new and improved magnetic dry reed switch which overcomes the limitations of the prior art devices.

It is another object of this invention to provide a new and improved magnetic dry reed switch which utilizes uniquely shaped, non-parallel, normally closed reed contacts for minimizin mutual capacitance while maintaining the desired overlap between the reed contacts.

It is still another object of this invention to provide a novel magnetic dry reed switch having a unique arcuate contact configuration which enhances the flux concentration at the normally closed contacts so as to provide a maximum repelling force therebetween upon application of a switching current to the switch coil.

It is a further object of this invention to provide such an improved magnetic single pole, double throw, dry reed switch in which the three reed contact construction and configuration is such as to enable a maximum contact gap to be maintained in either the energized or deenergized condition of the switch.

It is a still further object of this invention to provide an improved'single pole, double throw, dry reed switch having a pair of relatively unyielding outer reed contacts and a relatively flexible inner switching reed contact, all formed of magnetic material, and having a unique configuration to enhance the restoring force of the inner switching reed contact for minimizing contact sticking and improving the power handling capacity of the reed contacts.

It is still another object of this invention to provide a new and improved single pole, double throw, dry reed switch characterized by its miniature size and high reliability.

3,229,063 Patented Jan. 11, 1966 The novel features which are characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a perspective view, with the tube envelope partially broken away, of an illustrative single pole, double throw, dry reed switch embodying the present invention;

FIGURE 2 is a side elevational view of the illustrative dry reed switch;

FIGURE 3 is a cross-sectional view of the dry reed switch, illustrating the configuration of the reed contacts, taken substantially as shown along line 33 of FIG- URE 2; and

FIGURE 4 is a view illustrating the miniature size of the inventive reed switch and the manner in which a plurality of switching functions can be effected with a single control coil.

Referring now to the drawing, and more particularly to FIGURES 1 and 2 thereof, there is shown one illustrative embodiment of a three reed, single pole, double throw, magnetic reed switch constructed in accordance with the present invention. The reed switch 10 comprises an elongated vessel or tube 12 which may either be evacuated or gas filled in the manner well known in the art.

Positioned within the sealed tube 12 are the three particularly shaped reed contacts which include the novel features of the present invention. Advantageously, for reasons brought out in greater detail hereinbelow, all three reed contacts are formed of magnetic material, as for example, Niron 5 2 or the like.

The first reed contact 14 includes a terminal portion 16 which extends through one end of the sealed tube 12 and a contact portion 20 positioned within the sealed tube 12. The contact portion 29 of reed contact 14 is relatively short and is formed of a flattened cross sec tion such that it is relatively stiff and unyielding to bending or movement in response to applied electromagnetic fields. The reed contact 14 will be referred to hereinbelow as the normally open contact of the reed switch 10;

The second reed contact 22 has a terminal portion 24 which extends through the sealed tube 12'anda relatively longer contact portion 28, Contact portion 23 of reed contact 22 also is formed with a flattened crosssectional configuration and the thickness of contact portion 28 is reduced, as at 2d, to render it flexible for move-. ment in an up or down direction as illustratedin FIG- URE 2 in response to the presence of electromagnetic fields.

The third reed contact 30 is formed with a terminal portion 32, which extends through the sealed tube 12; and a flattened contact portion 34. As particularly shown in FIGURES 1 and 2, the contact portion 34 of reed contact 30 is longitudinally linear and is inclined at an acute angle with respect to the contact portion 28 of reed contact 22. The inner end of contact portion 34 of reed contact 3% is formed with an arcuate configuration 36 which curves upwardly from the contact portion 23 of reed contact 22 such that the arcuate configuration 36 is tangential to the contact portion 28 when these two reed contacts are in their normally closed condition. Hereinbelow reed contacts 22 and 30 will be referred to as the normally closed contacts since reed contact 30 is pre-tensioned to be in abutting, closed circuit engagement with reed contact 22-, as described above, in the absence of a switching electromagnetic field being applied to the reed switch 10.

Since the contact portions and 34 of the outer reed contacts 14 and 30, respectively, are relatively stiff with respect to the flexible contact portion 28 of the switching reed contact 22, the outer reed contacts remain generally stationary and only the switching reed contact 22 is moved in response to the application of an electromagnetic field to provide the switching function. While no electromagnetic coil has been shown in FIGURES 1 and 2, it will be understood by those skilled in the art that the electromagnetic field for effecting the switching function may be supplied by suitable electrically energized coil positioned around the sealed tube 12, as for example, the electrically energized coil 33 shown in FIGURE 4 and described hereinbelow.

The many advantages arising from the construction and use of the inventive reed switch will now be described. Those skilled in the art will appreciate that prior art reed switches, as exemplified by the Ellwood and Karrer patents identified above, are characterized by the presence of a high mutual capacitance between the reed contacts. Manifestly, this high mutual capacitance is undesirable in certain applications of reed switches involving high frequency radio waves or electronic devices where the capacitances between the reed contacts must be kept to a minimum. In accordance with a feature of this invention, the capacitance between the normally closed reed contacts 22 and 30, when in their open state, is substantially minimized to enable the invention to be used in high frequency environments without difficulty. This desirable result is achieved by the particular configuration of the angled or inclined portion 34 and the arcuate end portion 36 of the reed contact 30.

In addition, this particular configuration of the reed contact substantially enhances the make and break switching action of the reed contacts.

As stated hereinabove, the reed contact 14 has a contact portion 20 which is shortened and is unyielding, while the reed contact 39 has a contact portion 34 which, while longer than contact portion 20, also is stiffened and unyielding. The contact portion 23 of the switching contact 22 is much more flexible than the outer contacts due to the reduced thickness portion 26 adjacent the flattened contact portion 28. It also should be noted that the flattened contact portion 28 of the switching contact 22 has been achieved without any change in the crosssectional area of the contacts so as to maintain full magnetic efficiency.

Since the reed contact portion 34 is not flexible, virtually all of the pre-tensioned forces which exist between the reed contacts 22 and 30 result in a build-up in the restoring spring rate in the switching contact 22, with almost no deflection in the outer spring contact 30 when a magnetic field is applied to the switch. This increased restoring force in the contact portion 28 of the switching contact 22 when the electromagnetic field is removed from the tube serves to considerably improve the power handling capacity of the switch contacts since sticking or minute contact welds are more easily broken, and the switching reed contact 28 return to its normally closed position more rapidly.

It also is a feature of this invention that the particular configuration of the normally closed contacts results in a concentration of the magnetic flux at the normally closed contacts where the arcuate portion 36 of the reed contact 30 tangentially abuts the contact portion 28 of the switching reed contact 22. If the reed contacts were parallel to each other for their entire length, as is typical in prior art devices, the available flux would be spread and diffused over relatively large and parallel surface areas. Since any magnetic forces developed in a reed contact near the tube seal are ineffective because of their proximity to the pivoting point, the magnetic switching action is not as efficient as it could be. In the present invention, the particular arcuate configuration of the reed Contact 30 results in a concentration of the magnetic flux at the contact portions 28 and 34 to provide a much more eificient switching action.

Thus, when the switching electromagnetic field is ap plied to the tube, as by means of an electrically energiz'- able coil, the contact reeds 22 and 30 assume one polarity, while the contact reed 14 assumes an opposite polarity. Thus, simultaneously, the contact portion 28 of the switching reed contact 22 is repelled by the contact reed 3t] while being attracted by the contact reed 14. Since contact reeds 14- and 30 are relatively stiff, the contact portion 28 of switching reed 22 will move from the normally closed contact to the normally open contact to effect a circuit switching function. When the electromagnetic field fiux is terminated, the contact portion 23 of switching reed 22 will return to its normally closed position, with the aid of the restoring force discussed above. Since the contact reed 30 is also formed of mag netic material, which advantageously may not be fully annealed, it will retain a sufficient amount of residual flux to provide magnetic dampening when the switching reed is restored and thereby minimizing contact bounce.

In addition to the above-discussed advantages, the novel configuraton of the contact reeds in the present inventi-on also serves to maintain a maximum gap between the contacts in either the energized or the de-energized condition of the switch. Those skilled in the art will appreciate that small contact gaps are undesirable in actual operation. An additional advantage of the present invention arises from the cross-sectional configuration of the contact portions 28 and 36 of reed contacts 22 and 30, respectively. As particularly shown in FIGURE 3 of the drawing, the surface of contact portion 28 adjacent the contact portion 36 is provided with an arcuate or rounded configuration which tangentially contacts the lower planar surface of the contact portion 36 of reed contact 30. The rounded configuration of contact portion 28 serves to eliminate the need to have these reed contacts in perfect face-to-face alignment. Thus, the contact reeds 14 and 22 are aligned using techniques familiar to those skilled in the art, and the alignment of contact reeds 22 and 30, because of the round to flat arrangement, is permitted to assume an alignment governed by reasonable manufacturing tolerances.

FIGURE 4 illustrates the extremely major size that can be achieved in a single pole, double throw reed relay when constructed in accordance with the present invention. As there illustrated, a plurality of the inventive reed relays It) can be inserted Within the single energizing coil 38 to enable the plurality of switching functions to be effected under the control of a single coil.

In accordance with a further feature of this invention, it also is contemplated that the switching reed contact 22 may be assembled so as to be in mid-position between the outer two contacts such that all contacts are in open circuit condition. With such an arrangement, the magnetic field flux may be induced by a permanent magnet or an electrically energizable coil to close either of the outer reed contacts with the switching contact so as to provide a differential relay.

It also is contemplated that the relationship of the reeds may be adjusted, either prior to or during assembly, such that the gap between reed contacts 14 and 22 and the stressed force between reed contacts 22 and 30 provide the following action. Upon application of the predetermined current through the energizing coil, the switching reed contact 28 separates from the reed contact 34, and remains suspended between the outer reed contacts without touching either. Upon application of an additional current to the energizing coil, the switching reed contact 28 then makes contact with the contact portion 20 of reed contact 14 One of the many useful applications of this particular embodiment is as a remote sensing alarm where increase or decrease in current levels Would be detected, and a' contact closure made to set off an alarm, as in a meter relay, for example.

While there has been shown and described a specific embodiment of the present invention, it will, of course, be understood that various modifications and alternative constructions may be made without departing from the true spirit and scope of the invention. Therefore, it is intended by the appended claims to cover all such modifications and alternative constructions as fall within their true spirit and scope.

What is claimed as the invention is:

1. The improvement of a single pole, double throw, magnetic reed switch comprising the combination of a sealed elongated tube, a plurality of reed contacts formed of magnetic material and having terminals extending through said tube for connection to an electrical circuit, said plurality of reed contacts including a first reed contact of relatively short, longitudinally linear configuration, said first reed contact being sufiiciently rigid to resist movement within the tube, a second reed contact of relatively long, longitudinally linear configuration, said second reed contact having a portion of reduced thickness to render it flexible for movement in response to the application of an electromagnetic field within the tube, and a third reed contact of relatively long extent, said third reed contact having a main portion inclined at an acute angle with respect to said second reed contact and having an end portion formed in an arcuate configuration tangential to said second reed contact, said second reed contact being positioned between said first and third reed contacts within said tube and being tensioned into normally closed contact engagement with said third reed contact, said reed contacts being so arranged that the application of a magnetic field within the tube results in mutual attracting forces between said first and second reed contacts and in mutual repelling forces between said second and third reed contacts to cause said second reed contact to move from said third reed contact toward said first reed contact to provide the desired contact switching action, the angular and arcuate configuration of said third reed contact relative to said second reed contact serving to concentrate the magnetic field flux at said contacts to maximize the mutual repelling forces therebetween and enhance the contact switching action.

2. The improvement of a single pole, double throw, magnetic reed switch comprising the combination of a sealed elongated tube, a plurality of reed contacts formed of magnetic material and having terminals extending through said tube for connection to an electrical circuit, said plurality of reed contacts including a first reed contact of relatively short, longitudinally linear configuration, said first reed contact being sufficiently rigid to resist movement Within the tube, a second reed contact of relatively long, longitudinally linear configuration, said second reed contact having a portion of reduced thickness to render it flexible for movement in response to the application of an electromagnetic field within the tube, and a third reed contact of relatively long extent, said third reed contact having a main portion inclined at an acute angle with respect to said second reed contact and having an end portion formed in an arcuate configuration tangential to said second reed contact, said second reed contact being positioned between said first and third reed contacts within said tube, said reed contacts being so arranged that the application of a magnetic field within the tube results in the desired contact switching action, the angular and arcuate configuration of said third reed contact relative to said second reed contact serving to enhance the contact switching action.

3. The improvement of a single pole, double throw, magnetic reed switch comprising the combination of a sealed elongated tube, a plurality of reed contacts formed of magnetic material and having terminals extending through said tube for connection to an electrical circuit, said plurality of reed contacts including a first reed contact of relatively short, l-ongitudinaly linear configuration, said first reed contact being sufiiciently rigid to resist movement within the tube, a second reed contact of relatively long, longitudinally linear configuration, said second reed contact having a portion of reduced thickness to render it flexible for movement in response to the application of an electromagnetic field within the tube, and a third reed contact of relatively long extent, said third reed contact having a main portion inclined at an acute angle with respect to said second reed contact and having an end portion formed in an arcuate configuration tangential to said second reed contact, said second reed contact being positioned between said first and third reed contacts within said tube, said reed contacts being so arranged that the application of a magnetic field within the tube results in mutual attracting forces between said first and second reed contacts and in mutual repelling forces between said second and third reed contacts to cause said second reed contact to move to said first reed contact to provide the desired contact switching action, the angular and arcuate configuration of said third reed contact relative to said second reed contact serving to concentrate the magnetic field flux at said contacts to maximize the mutual repelling forces therebetween and enhance the contact switching action.

4. The improvement of a single pole, double throw, magnetic reed switch comprising the combination of a sealed elongated tube, a plurality of reed contacts formed of magnetic material and having terminals extending through said tube for connection to an electrical circuit, said plurality of reed contacts including a first reed contact of relatively short, longitudinally linear configuration, said first reed contact being sufficiently rigid to resist movement within the tube, a second reed contact of relatively long, longitudinally linear configuration, said second reed contact having a portion of reduced thickness to render it flexible for movement in response to the application of an electromagnetic field within the tube, and a third reed contact of relatively long extent, said third reed contact having a main portioninclined at an acute angle with respect to said second reed contact and having an end portion formed in an arcuate configuration tangential to said second reed contact, said second reed contact being positioned between said first and third reed contacts Within said tube and being tensioned into normally closed contact engagement with said first reed contact, said reed contacts being so arranged that the application of a magnetic field within the tube results in mutual attracting forces between said first and second reed contacts and in mutual repelling forces between said second and third reed contacts to cause said second reed contact to move from said third reed contact to said first reed contact to provide the desired contact switching action, the angular and arcuate configuration of said third reed contact relative to said second reed contact serving to concentrate the magnetic field flux at said contacts to maximize the mutual repelling forces therebetween and enhance the contact switching action, and means for eliminating the need to maintain said second and third reed contacts in perfect face-to-face alignment when these contacts are in the normally closed condition by forming the surface of said second reed contact adjacent said third reed contact with an arcuate configuration which is tangential to the surface of said second reed contact when the latter are in their normally closed position.

5. The improvement of a single pole, double throw, magnetic reed switch comprising the combination of a sealed elongated tube, a plurality of reed contacts formed of magnetic material and having terminals extending through said tube for connection to an electrical circuit, said plurality of reed contacts including a first reed contact of sufiicient rigidity to resist movement within the tube, a second reed contact having a portion of reduced thickness sufficient to render it flexible for movement in response to the application of an electromagnetic field within the tube, and a third reed contact, said third reed contact having a main portion inclined at an acute angle with respect to said second reed contact and having an end portion formed in an arcuate configuration tangential to said second reed contact, said second reed contact being positioned between said first and third reed contacts within said tube, said reed contacts being so arranged that the application of a magnetic field within the tube results in the desired contact switching action, and means for eliminating the need to maintain said second and third reed contacts in perfect face-to-face alignment when these contacts are in their closed condition by forming the surfaw of said second reed contact adjacent said third reed contact with an arcuate configuration which is tangential to the surface of said third reed contact when the latter are in their closed position.

References Cited by the Examiner UNITED STATES PATENTS 2,450,499 10/1948 Brown 200- 87 2,483,723 10/1949 Burton 200-87 2,892,052 6/1959 Ducati 20087 2,922,856 1/1960 'Karrer 200- 87 3,146,327 8/1964 Yoshitarni Ohki et al. 200-166 3,165,608 1/1965 Wallace 200-87 OTHER REFERENCES Bradford, K, E: An Experimental Dry-Reed Sealed Transfer Contact, in Bell Laboratories Record, May 1963, pp. 200202.

15 BERNARD A. GILHEANY, Primary Examiner.

B. DOBECK, Assistant Examiner. 

1. THE IMPROVEMENT OF A SINGLE POLE, DOUBLE THROW, MAGNETIC REED SWITCH COMPRISING THE COMBINATION OF A SEALED ELONGATED TUBE, A PLURALITY OF REED CONTACTS FORMED OF MAGNETIC MATERIAL AND HAVING TERMINALS EXTENDING THROUGH SAID TUBE FOR CONNECTION TO AN ELECTRICAL CIRCUIT, SAID PLURALITY OF REED CONTACTS INCLUDING A FIRST REED CONTACT OF RELATIVELY SHORT, LONGITUDIALLY LINEAR CONFIGURATION, SAID FIRST REED CONTACT BEING SUFFICIENTLY RIGID TO RESIST MOVEMENT WITHIN THE TUBE, A SECOND REED CONTACT OF RELATIVELY LONG, LONGITUDINALLY LINEAR CONFIGURATION, SAID SECOND REED CONTACT HAVING A PORTION OF RREDUCED THICKNESS TO RENDER IT FLEXIBLE FOR MOVEMENT IN RESPONSE TO THE APPLICATION OF AN ELECTROMAGNETIC FIELD WITHIN THE TUBE, AND A THIRD REED CONTACT OF RELATIVELY LONG EXTENT, SAID THIRD REED CONTACT HAVING A MAIN PORTION INCLINED AT AN ACUTE ANGLE WITH RESPECT TO SAID SECOND REED CONTACT HAVING AN END PORTION FORMED IN AN ARCUATE CONFIGURATION TANGENTIAL TO SAID SECOND REED CONTACT, SAID SECOND REED CONTACT BEING POSITIONED BETWEEN SAID FIRST AND THIRD REED CONTACTS WITHIN SAID TUBE AND BEING TENSIONED INTO NORMALLY CLOSED CONTACT ENGAGEMENT WITH SAID THIRS REED CONTACTS WITHIN CONTACTS BEING SO ARRANGED THAT THE APPLICATION OF A MAGNETIC FIELD WITHIN THE TUBE RESULTS IN MUTUAL ATTRACTING FORCES BETWEEN SAID FIRST AND SECOND REED CONTACTS AND IN MUTUAL REPELLING FORCES BETWEEN SAID SECOND AND THIRD REED CONTACTS TO CAUSE SAID SECOND REED CONTACT TO MOVE FROM SAID THIRD REED CONTACT TOWARD SAID FIRST REED CONTACT TO PROVIDE THE DESIRED CONTACT SWITCHING ACTION, THE ANGULAR AND ARCUATE CONFIGURATION OF SAID THIRD REED CONTACT RELATIVE TO SAID SECOND REED CONTACT SERVING TO CONCENTRATE THE MAGNETIC FIELD FLUX AT SAID CONTACTS TO MAXIMIZE THE MUTUAL REPELLING FORCES THEREBETWEEN AND ENHANCE THE CONTACT SWITCHING ACTION. 